System for and method of image reconstruction with dual line scanner using line counts

ABSTRACT

A fingerprint scanning and image reconstruction system and method including a fingerprint scanner providing a first scan line and a second scan line separated by a line separation distance in a scanning direction. The system includes an image reconstruction module accumulating scan lines including at least the first scan line and the second scan line over a time period t. The image reconstruction module a value for decimation (t) necessary to produce a selected y axis resolution in the scanning direction based at least in part on (line count(t)/line separation distance)* a selected y resolution, where line count(t) is the number of lines accumulated in time t, and decimation(t) indicates of whether the line count(t) is greater than or less than the number of lines accumulated as a function of the time period t that will result in a selected reconstructed image y resolution in the scanning direction.

BACKGROUND OF THE INVENTION

Some conventional fingerprint scanners include large, wall-mountedunits, called contact or placement sensors, that sense an entirefingerprint at once (e.g., an entire fingerprint including images of200-500 rows and 128-200 columns of pixels). Other fingerprint scannersinclude smaller swipe scanners incorporated into laptop and notebookcomputers, mobile phones, mobile email devices, and smart phones.Smaller swipe scanners are much less expensive to manufacture thanlarger contact or placement scanners. Stationary swipe fingerprintscanners sense a finger being swiping across the scanner and can be dualline scanners or multi line scanners.

One example of a dual line scanner is disclosed in U.S. Pat. No.6,002,815 issued to Immega et al. on Dec. 14, 1999 (“Immega”), theentire contents of which is herein incorporated by reference. The Immegadual line scanner must determine and track the velocity of the finger asit passes over the sensor and a 1×n pixel array scanner. The Immega dualline scanner performs 1×n linear array cross-correlation on current andhistoric line scans to initially image the fingerprint. The velocity ofthe finger must then be known in order to reconstruct the fingerprintimage from the line scans.

One example of a multi line scanner is disclosed in U.S. Pat. No.7,197,168, issued to Russo on Mar. 27, 2007 (“Russo”), the entirecontents of which is herein incorporated by reference. The Russo multiline scanner reassembles overlapping object imaging frame scanscollected by a multi line sensor array to reconstruct the fingerprintimage without calculating the velocity of the finger.

SUMMARY OF THE INVENTION

Determining and tracking the velocity of the finger as it moves over thescanner is cumbersome and require additional system complexity toaddress special cases such as stiction, dropped lines and line culling.Thus, there is a need for a dual line scanner for imaging a fingerprintthat does not require velocity to be determined.

Some embodiments of the present disclosure provide a fingerprintscanning and image reconstruction system and method to createfingerprint images without relying on velocity. The system can include afingerprint scanner providing a first scan line and a second scan lineseparated by a line separation distance in a scanning direction. Thesystem can include an image reconstruction module receiving andaccumulating scan lines including at least the first scan line and thesecond scan line over a time period t. The image reconstruction moduledetermines a reconstructed image resolution in the scanning directionbased at least in part on [line separation distance divided by linecount(t)] multiplied by decimation(t), where line count(t) is the numberof lines accumulated as a function of the time period t, anddecimation(t) is a ratio indicative of whether the line count(t) isgreater than or less than the number of lines accumulated as a functionof the time period t that will result in a selected reconstructed imageresolution in the scanning direction.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 is a schematic block diagram of a basic configuration for afingerprint scanning and image reconstruction system according toembodiments of the present disclosure.

FIG. 2 is a schematic view, partly in block diagram form, of a dual linefingerprint scanner according to one embodiment of the presentdisclosure.

FIG. 3 is a flow diagram for an image reconstruction process accordingto one embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Before any embodiments of the invention are explained in detail, it isto be understood that the present disclosure is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in thedescribed drawings. The present disclosure is capable of otherembodiments and of being practiced or of being carried out in variousways. Also, it is to be understood that the phraseology and terminologyused in this application is for the purpose of description and shouldnot be regarded as limiting. The use of “including,” “comprising,” or“having” is meant to encompass the items listed thereafter andequivalents, as well as additional items. Unless specified or limitedotherwise, the terms used are intended to cover variations ordinarilyknown, now or in the future. Further, “connected” and “coupled” are notrestricted to physical or mechanical connections or couplings and caninclude both physical and electrical, magnetic, and capacitive couplingsand connections.

The following discussion is presented to enable a person skilled in theart to make and use embodiments of the present disclosure. The followingdetailed description is to be read with reference to the figures, inwhich like elements in different figures have like reference numerals.The figures depict selected embodiments and are not intended to limitthe scope of embodiments of the present disclosure.

FIG. 1 schematically illustrates a fingerprint scanning and imagereconstruction system 200 according to embodiments of the presentdisclosure. The fingerprint scanning and image reconstruction system 200includes a sensor 202 and an image reconstruction module 204. The imagereconstruction module 204 can be connected to or integrated with a hostcomputing device 206 (as shown in FIG. 2) and can receive inputs fromthe sensor 202. The host computing device 206 can be connected to adatabase 210. In some embodiments, the sensor 202 can also include aculling module 205 to reduce the amount of data transmitted over thebandwidth of the communication links, whether wired or wireless, betweenthe sensor 202, the image reconstruction module 204, and the hostcomputing device 206. Culling is a technique for keeping line scans withvery little variation from one clock time to the next clock time frombeing sent to the image reconstruction module 204 and/or the hostcomputing device 206. If there is no change from one clock time to thenext clock time, the finger is not moving with respect to the sensor202. It is well understood in the art that such essentially redundantscan lines are not useful in image reconstruction. Note that the imagereconstruction system 200 may be implemented across multiple discretedevices or on a single piece of silicon.

FIG. 2 schematically illustrates a dual line fingerprint scanner 220according to one embodiment of the present disclosure. The dual linescanner 220 includes a primary linear scanner segment 230 and asecondary linear scanner segment 250. The primary linear scanner segment230 can be a 1×n linear pixel array, where n is typically 128-200 pixelscan points (for illustrative purposes, only 12 pixel scan points 232are shown in FIG. 2). The secondary linear scanner segment 250 can be a1×n linear pixel array, where n is about half of the number of pixels inthe primary linear scanner segment 230 (e.g., about 64-100 pixel scanpoints 252, but with only 6 pixel scan points 252 being shown in FIG.2). The secondary linear segment 250 need not be centered with respectto the primary segment 230, but in fact may span any physical subset ofthe primary segment 230.

Drive signals are supplied to each pixel scan point 232, 252 throughleads 234, 254 across from reference voltage plates 236, 256 using amultiplexer 270, connected to the leads 234, 254 through contacts 262.The responses to the drive signals are influenced by capacitivecouplings between the leads 234, 254 and the voltage plates 236, 256 atthe pixel scan points 232, 252 as sensed by sensors 272. The capacitivecouplings are influenced by whether the portion of the fingerprint beingscanned at the pixel scan points 232, 252 is a ridge or a valley of thefingerprint. The output of each pixel scan point 232, 252 is a grayscale value from zero to 255. This is a convenient byte size data valuerange that is exemplary only and can be other values of gray scalegranularity, such as using 4 bits instead of 8 bits per pixel.Typically, the gray scale value of zero is white and the gray scalevalue of 255 is black, with intervening incremental shades of graybetween these values. The image reconstruction module 204 can performimage reconstruction using these scan lines and the gray scale values toreconstruct the fingerprint with dark indicating ridges and lightindicating valleys.

The goal of image reconstruction with a single line scanner or the dualline scanner 220 is to create a fingerprint image with fixed resolutionin the y direction. The value of n in the primary linear scanner segment230 (e.g., n=128) determines the resolution in the x direction. Withcurrently existing systems having 128-200 pixels in the x direction, theleads 234, 254 are typically 25 μm in width with spaces 238, 258 betweenthe leads 234, 254 being 25 μm. Therefore, x-resolution, determined bythe distance between the centers of leads 234, is 50 um typically (whichgives us 508 dpi). This distance “R” is shown in FIG. 2 for both theprimary linear scanner section 230 and the secondary liner scannersection 250. For illustration purposes, +y is chosen to be in thedirection the finger moves across the secondary linear scan segment 250first and then over the primary linear scan segment 230, i.e., SP asshown in FIG. 2, and −y is chosen to be in the direction the fingermoves over the primary linear scan segment 230 first and then over thesecondary linear scan segment 250, i.e., PS (up as shown in thearrangement of FIG. 2). Typically y-resolution is chosen to equalx-resolution, but y-resolution may be chosen arbitrarily depending onother system attributes.

For illustration purposes, the y resolution in a reconstructed image canbe measured in unit distance/row (e.g., μm/row=μm/sample). In otherwords, at the given clock speed for the pixels 232, 252, a row issubstantially equivalent to a sample taken at each sample time, dictatedby the clocking of the sampling scanners (i.e., the pixel scan points232, 252 in each of the primary linear scanner segment 230 and thesecondary linear scanner segment 250). Alternatively, this could beexpressed in a more familiar row/unit distance desired in the recreatedimage to obtain a desired dots per inch (dpi) image resolution in the ydirection (e.g., 508 rows/inch=508 samples/inch for a 508 dpiresolution, which corresponds to a scan line separation of 50 μm persample). Assuming a separation of the primary linear scanner segment 230from the secondary linear scanner segment 250 of eight rows, this isequal to a 400 μm separation between the scanned image line from theprimary linear scanner segment 230 to the secondary linear scannersegment 250 for each sample time.

The mathematical equation for a single or dual line sensor without lineculling is the following equation (i):Image Y-resolution=[Velocity(t)*Decimation(t)]/SensorSampleRate  (i)where time period t is the time it takes for the finger to move from thesecondary to the primary (or vice versa), Velocity(t) is the fingervelocity during time period t with respect to the primary and secondarylinear scanner segments 230, 250; SensorSampleRate is the sensor's fixedscan line rate (i.e., sample timing); and Decimation(t) is thedecimation or interpolation ratio required to obtain the desiredy-resolution during time period t; it is unitless. A decimation value of1 means no decimation or interpolation occurs in the imagereconstruction (i.e., the object being scanned uniformly passed theprimary and secondary linear scanner segments 230, 250 at exactly thevelocity needed to obtain the desired y resolution for the desired dpi.A value of greater than 1 implies some scan lines are not used in thereconstructed image (i.e., decimation needs to be done). A value of lessthan 1 implies some scan lines are added to the reconstructed image(i.e., interpolation needs to be done). In this equation thereconstruction algorithm needs first to estimate the finger velocityover each time period t, after which the decimation rate may then becalculated using the above equation in order to properly resample thescan lines into a fixed-resolution reconstructed image.

Since the sample rate is constant, once velocity is calculated using thedual scan lines, the decimation ratio is trivial to compute. Resolutionis in μm/row, velocity is in μm/sec, and sample rate is in rows/sec.Velocity divided by sample rate is in μm/row, since the decimation ratiois unitless. Therefore, the image reconstruction unit 204 simply needsto calculate the correct Decimation(t) and resample the scan line datait receives (i.e., perform decimation or perform interpolation asneeded, or perform neither).

With the first equation (i), it can be seen that as the fingerprintbeing scanned moves more quickly, the decimation ratio must change in aninversely proportional way to velocity to result in a constant outputresolution. This is what is used in conventional single and dual linescanners for image reconstruction to determine what is known as“required resampling.” However, with line culling, the effective samplerate is a variable (i.e., dependent on time as well). Therefore, thegoverning second equation (ii) is as follows:ImageY-resolution=[Velocity(t)*Decimation(t)]/EffectiveSampleRate(t)  (ii)

As the finger velocity changes, the nature of culling is that it islikely to change in a proportional way. For example, as velocity goesdown, the effective sample rate also goes down because fewer lines aresent. Stiction, where the finger moves very slowly or stops moving, isan extreme example of this. During stiction, the decimation factor stillmay change with time (because culling is not perfect), but it is also nolonger guaranteed to be inversely proportional to velocity. Withconventional image reconstruction methods, it is necessary to modify thetimestamps attached to each scan during stiction to remove the longdelay between received scan lines due to culling, which allows theproper resampling to occur.

According to embodiments of the present disclosure, resampling is notrequired if the correct equations are used. As an extreme example, thefinger is moving at the natural rate of the sensor, namely 50 μm/sec(i.e., 1 row per sample speed Δt interval), and for simplicity thesensor's sampling rate is 1 row/sec (i.e., one sample every 50 μm). Insuch a case, the decimation rate is always 1 and the imagereconstruction module 204 does not need to perform any resampling(decimation or interpolation).

In another extreme example, consider the finger stopping due to stictionfor 1 hour during which time culling correctly does not send any linesto the image reconstruction module 204. In this example, the finger thenimmediately resumes at the original 50 μm/sec velocity. During thestiction, due to the long delay in movement, the velocity calculationwill effectively be zero. Using the first equation (i), one may chooseto decimate greatly, which is incorrect. In fact, the correct answer isto do nothing but stack the received scan lines. If the second equation(ii) were being used, the decline in velocity would be offset by thedecline in effective sample rate, and the decimation would have remainedconstant at 1.

According to embodiments of the present disclosure, there is a moreeffective way to address these issues with image reconstruction as it iscurrently implemented. Even if using what currently may be determined tobe the correct equation, a velocity calculation still appears to berequired. However, embodiments of the present disclosure use imagereconstruction equations that do not require a velocity calculation. Thefollowing is the second equation (ii):ImageY-resolution=[Velocity(t)*Decimation(t)]/EffectiveSampleRate(t)  (ii)

The second equation (ii) can be refactored as follows into equation(iii):ImageY-resolution=[Velocity(t)/EffectiveSampleRate(t)]*Decimation(t)  (iii)

The secondary linear scanner segment 250 of the dual line scanner 220has been used solely to determine velocity, which is why equations (i),(ii), and (iii) also apply to a single line scanner that has somealternate way of calculating instantaneous velocity. When a rowpreviously seen on the secondary linear scanner segment 250 reaches theprimary linear scanner segment 230 (i.e., the finger is sweeping acrossthe secondary linear scanner segment 250 first), the velocitycalculation is performed as follows according to equation (iv):Velocity(t)=LineSeparation/ElapsedTime(t)  (iv)

where LineSeparation is for example 400 μm (i.e., 8 rows) andElapsedTime(t) is the amount of time it took for the finger to move fromthe secondary linear scanner segment 250 to the primary linear scannersegment 230 (or vice versa). This relationship would be inverselyproportional if the velocity is high enough such that the sensor 202 isundersampled, in which case no culling should occur andEffectiveSampleRate(t) can safely be replaced by SensorSamplingRate.While ElapsedTime(t) may actually be calculated using sensor timestamps,which are really line counts, and multiplying by some fixedSensorSamplingRate, it does not cancel out the EffectiveSampleRate(t)factor in the denominator.

Inserting equation (iv) into the second equation (ii) gives thefollowing equation (v):ImageY-resolution=[LineSeparation/{ElapsedTime(t)*EffectiveSampleRate(t)}]*Decimation(t)  (v)

However, it can be seen that EffectiveSampleRate(t) is actually thenumber of rows received by the image reconstruction module 204 dividedby the time it took to move from the secondary linear scanner segment250 to the primary linear scanner segment 230, which equals theElapsedTime. Thus, ElapsedTime(t)*EffectiveSampleRate(t) is simply thenumber of rows received by the image reconstruction module 204 in thattime. Therefore, the new image reconstruction equation (vi) is asfollows:

$\begin{matrix}\begin{matrix}{{{Image}\mspace{14mu} Y\text{-}{resolution}} = {\left\lbrack {{LineSeparation}/{{LineCount}(t)}} \right\rbrack*}} \\{{{{Decimation}(t)}\mspace{14mu}{or}},{reorganized},{{Decimation}(t)}} \\{= {\left( {{{Image}\mspace{14mu} Y} - {{resolution}*{Line}\mspace{14mu}{Count}\mspace{14mu}(t)}} \right)/}} \\{{Line}\mspace{14mu}{Separation}}\end{matrix} & ({vi})\end{matrix}$

As can be seen, there is no velocity calculation in the new imagereconstruction equation (vi). If 8 rows were received by the imagereconstruction module 204 in the time it took to move from the secondarylinear scanner segment 250 to the primary linear scanner segment 230,and the line separation between the two is 8 rows, the decimation ratiois 1 and no re-sampling needs to be done for image reconstruction. If 16lines are received, the decimation factor=2 and half of the receivedlines will be thrown away (i.e., decimated) in order to maintain aconstant 508 dpi resolution. If only 4 lines are received, the imagereconstruction module 204 must interpolate (i.e., add in) another 4lines to maintain the required 508 dpi resolution. Using the aboveequation only decimation rate needs to be calculated; velocity is notneeded as it has been substituted by the line count, which is trivial toobtain.

Revisiting the extreme example of the finger stopping for 1 hour in themiddle of a swipe due to stiction (the same applies for lesser amountsof stiction, but the extreme amount is illustrative of the effects), nomatter how long it takes, the image reconstruction module 204 willreceive 8 lines. Due to the assumption that the finger when it isactually moving, moves at 50 μm/sec, the image reconstruction module 204will receive 8 scan lines from the sensor 202 (again assuming perfectculling). Therefore, the line count is 8 rows, the line separation is400 μm, and the decimation is 1, in order to maintain 50 μm/row.

According to embodiments of the present disclosure, an improved versionof image reconstruction can use the new image reconstruction equation(vi) to perform resampling to match the actual number of scanned linesto the desired number of scanned lines and it will not be necessary tocompute instantaneous velocity. Therefore, the improved way ofperforming image reconstruction is very different from the prior art,which clearly requires the use of velocity for image reconstruction. Thesoftware used to implement equation (vi) is more simple and thecomputing requirements are reduced. Stiction will not need to beaccounted for and the use of timestamp modifications is renderedunnecessary. Improved fidelity of the reconstructed image may also proveto be a result in some cases.

FIG. 3 illustrates an object imaging process according to embodiments ofthe present disclosure. The sensor 202 can be used (at 302) to scan theprimary and secondary scan lines. The image reconstruction module 204can accumulate (at 304) the scan lines. The image reconstruction module204 can then determine (at 306) the y-axis resolution from equation(vi), i.e., [line separation/line count (t)]*decimation (t). The imagereconstruction unit 204 can then reconstruct (at 308) the image.

Embodiments of the present disclosure can be used to scan objects otherthan fingers and to create images of such objects other than fingerprintimages. The present disclosure can be used to scan other biometric data,such as the palm of a hand or a retina. The present disclosure can alsobe used to scan virtually any type of object by a swipe scan withouthaving to calculate the velocity of the object as it moves across theswipe scanner.

The present disclosure is described with reference to block diagrams andoperational illustrations of methods and devices implementing methods(collectively “block diagrams”). Each block of the block diagram, andcombinations of blocks in the block diagram, can be implemented withanalog or digital hardware and/or computer program instructions, such asin a computing device. The computer program instructions can be providedto a processor of a general purpose computer, special purpose computer,microcontroller, ASIC, or any other programmable data processingapparatus, so that the instructions implement the functions/actsspecified in the block diagram when executed via the computing device.The functions/acts noted in the blocks can occur out of the order notedin the block diagram. For example, two blocks shown in succession can infact be executed substantially concurrently or the blocks can sometimesbe executed in the reverse order, depending upon the functionality/actsinvolved. In addition, different blocks may be implemented by differentcomputing devices, such as an array of processors within computingdevices operating in series or parallel arrangement, and exchanging dataand/or sharing common data storage media.

The term “computer readable medium” as used herein and in the claimsgenerally means a non-transitory medium that stores computer programsand/or data in computing device machine-readable form. Computer readablemedium can include computer storage media and communication media.Computer storage media can include volatile and non-volatile, removableand non-removable media implemented with any suitable method ortechnology for the storage of information, such as computer-readableinstructions, data structures, program modules, or specificapplications.

The term “module” as used herein and in the claims generally means asoftware, hardware, and/or firmware system, process and/or functionalitythat can perform or facilitate the processes, features, and/or functionsof the present disclosure, with or without human interaction oraugmentation. A module can include sub-modules. Software components of amodule can be stored on a non-transitory computing device readablemedium. Modules can be integral to one or more servers or can be loadedand executed by one or more servers. One or more modules can be groupedinto an engine or an application.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A fingerprint scanning and image reconstructionsystem comprising: a fingerprint scanner providing a first scan line anda second scan line separated by a line separation distance in a scanningdirection; and an image reconstruction module in communication with thefingerprint scanner, the image reconstruction module receiving scanlines including at least the first scan line and the second scan line,the image reconstruction module accumulating scan lines over a timeperiod t; the image reconstruction module determining a value fordecimation (t) necessary to produce a selected y axis resolution in thescanning direction based at least in part on (line count(t) divided byline separation distance) times the selected y resolution, where linecount(t) is the number of lines accumulated as a function of the timeperiod t, and decimation(t) is a ratio indicative of whether the linecount(t) is greater than or less than the number of lines accumulated asa function of the time period t that will result in the selectedreconstructed image y resolution in the scanning direction.
 2. Thesystem of claim 1 wherein the image reconstruction module is adapted toremove scan lines from a reconstructed image when the decimation(t)ratio is greater than 1 and to add interpolated scan lines to thereconstructed image when the decimation(t) ratio is less than
 1. 3. Thesystem of claim 1 wherein the first scan line and second scan line eachinclude a plurality of pixel scan points from a linear scanner array. 4.The system of claim 1 wherein the fingerprint scanner is a dual linescanner.
 5. The system of claim 4 wherein the dual line scanner includesa primary linear scanner segment and a secondary linear scanner segment.6. The system of claim 1 and further comprising a sensor incommunication with the fingerprint scanner and the image reconstructionmodule.
 7. The system of claim 6 wherein the sensor includes a cullingmodule to eliminate redundant scan lines.
 8. A method of scanning afingerprint of a finger moving in a scanning direction andreconstructing a fingerprint image, the method comprising: scanning afirst scan line and a second scan line separated by a line separationdistance in the scanning direction; accumulating scan lines including atleast the first scan line and the second scan line over a time period t;determining a value for decimation(t) necessary to produce a selected yaxis resolution in the scanning direction based at least in part on(line count(t) divided by line separation distance) times the selected yresolution, where line count(t) is the number of lines accumulated as afunction of the time period t, and decimation(t) is a ratio indicativeof whether the line count(t) is greater than or less than the number oflines accumulated as a function of the time period t that will result inthe selected reconstructed image y resolution in the scanning direction.9. The method of claim 8 and further comprising removing scan lines froma reconstructed image when the decimation ratio is greater than 1 andadding interpolated scan lines to the reconstructed image when thedecimation ratio is less than
 1. 10. The method of claim 8 and furthercomprising obtaining the first scan line and second scan line with aplurality of pixel scan points from a respective first linear scannerarray and second linear scanner array.
 11. A non-transitorycomputer-readable storage medium for tangibly storing thereon computerreadable instructions for a method of creating an image of a fingermoving in a scanning direction, the method comprising: receiving a firstscan line and a second scan line separated by a line separation distancein the scanning direction; accumulating scan lines including at leastthe first scan line and the second scan line over a time period t;determining a value for decimation(t) necessary to produce a selected yaxis resolution in the scanning direction based at least in part on(line count(t)/line separation distance)* the selected y resolution,where line count(t) is the number of lines accumulated as a function ofthe time period t, and decimation(t) is a ratio indicative of whetherthe line count(t) is greater than or less than the number of linesaccumulated as a function of the time period t that will result in theselected reconstructed image y resolution in the scanning direction. 12.The method of claim 11 and further comprising removing scan lines from areconstructed image when the decimation ratio is greater than 1 andadding interpolated scan lines to the reconstructed image when thedecimation ratio is less than
 1. 13. The method of claim 11 and furthercomprising obtaining the first scan line and second scan line with aplurality of pixel scan points from a linear scanner array.
 14. A methodof scanning an object of and reconstructing an image, the methodcomprising: scanning a first scan line and a second scan line separatedby a line separation distance in the scanning direction; accumulatingscan lines including at least the first scan line and the second scanline over a time period t; determining a reconstructed image resolutionin the scanning direction based at least in part on [line separationdistance divided by line count(t)] multiplied by decimation(t), whereline count(t) is a number of lines accumulated as a function of the timeperiod t, and decimation(t) is a ratio indicative of whether the linecount(t) is greater than or less than the number of lines as a functionof the time period t that will result in the selected reconstructedimage resolution in the scanning direction.
 15. The method of claim 14wherein the object is at least one of a fingerprint, a hand, and aretina.
 16. The method of claim 14 and further comprising removing scanlines from a reconstructed image when the decimation ratio is greaterthan 1 and adding interpolated scan lines to the reconstructed imagewhen the decimation ratio is less than
 1. 17. The method of claim 14 andfurther comprising obtaining the first scan line and second scan linewith a plurality of pixel scan points from a linear scanner array.